Relayed headlight harness for H4 headlights. Can be used with factory 9004 harness with just a single H4 adapter, since the harness only needs a single input for hi/low beams to function properly! Relayed with 40 amp relays. Huge difference in light output, especially for those older Mk1’s where it feels like you’re driving with a flashlight in front of you for headlights!!